Boiler feed water control system



Jan. 2, 1940. K. B. Howl-:LL

BOILER FEED WATER CONTROL SYSTEM Filed June 7, 1937 Patented Jan. f2, 194C BOILER; Elim), WATER coNrnoL .SYSTEM Kenneth Bj. Howell, Milwaukee, Application June -7v, 193'?,V Seriall No@ 146,867

l 4; Claims.

Tlfrisinventionr relates to control meansffor. con trolling the supplyr offfeed Water; tofsteamboilers.

The supply` of feed Waterto` steam-:boilers is customarily' regulated to` maintain a constant level in theboiler. In. generalthe supply; of feed Waterv isnow. automatically controlledA byf means utilizing; a- Valve in the; feed water supply `line which is arrangedfto beclosed er;r openedby motive equipment which. is responsive to, changes. in` boiler, Water level. The particular responsiveele- Y ment employed'may vary, but inall eventsgit, is

upon thesteam demand upon theboilerfbecauseone steam. demand is. reflected .in .the amount ofI feed Waterthat mustgbesupplied. For a: lowrate of-steam demand and acorrespondingly low rate. of feedvvatersupply. a highlevelof Water. must bemaintainedinthe boiler. Eor. highrates-iof feed Water. supply, a. lowf level lof.. Water becomes necessary in order tuy obtain..a..sucientj valve opening to. supply theamount of. water. required.y The. use of. a large Valve, permittinggvery. slight .A travel fora large variation in. Water supply, would correct this condition. Such.a.valvehowever, is impracticable` becausev of. the. oost and.A the increasing leakage Which accompaniesincreasein valve size. y

For efficient boiler."operation,y it. is desirable. that a close regulationv of water level. be. main-.1 tainedwhich will be relatively independent ofthe rat-e of feed Water supply. 'It is-theobjectof the presentinventicnto provideA means whereby this ff desirable result may be accomplished;

Since the rate of feedwater supply followsy closelyV the` rate ofA stream: output, I indthat'an'V arrangement may bamade whereby. theffed`` Water` supply, is controlled: byrmeans directly ref sponsive to the steamdelnand. Such an-arrangement approximates the service-requirements of normal boiler operation.

Other and merespeciiic objects vandadvantages `of the-'invention will appear-as thedescription proceeds reference being-had to the'accompany;

ing drawingvwherein.apreferred form of the in` Vention is shown. It' is to be understood, however,

that the drawing and descriptionare illustrative' only and are not to be taken as limiting the invention; exceptA in so far as it isllimited bythe claims.v

the drawing-v Fig. 1 is a somewhat diagrammatic View: il-

lustratingga. beiler equipped with; control. means Whichfernbodies the present.v invention; l

Fig, 2 is.l an enlgrged fragmentary View. of a bleed.v valvefernprloyedfin4 this-,- system'.V f t Referring now in.Y detail tothe drawing, the numeral 5 indicates.-.a.boilerV in, Which-steam; is

generated by any suitable. method... A- steam out,-

putcenduit it isutilized'to,draW-steam.from the boilerl '5. A-.feedn-Water inletconduitl isadapted to. supply feed Water to.Y the boiler 5,.y through a control. valve 8, ,a- Water level.l responsive valve Q, andamanually; operated shut ofvalve. I.

For purposes of illustration,.= show. herein a v float. mechanism. tI housedfina float: chamber I2 for. controlling` the supply of feed. water to the. boiler. 5-

response to Water. level Varia.- tions. The float. operatedtype of` water. level regulator shown. at. Il is. merely` a. conventional type. which. openseor closes. the valve. 9. in i response tachangesin. leyel of "Water in.- theboiler 'inthe :usual manner Withatconstant differential of'pnessuremaintainedacross.the vali/e. 9. v The rate oilew through thevalue is approximately. proportionalto theport area ofthisvalveatrany given valve positionor consequently, any given boiler level. Itrequiresa considerable changein.

` boiler. water. level to effect. a. changein, port area.

off-the valve lL, 'lliereforaifa greateramount Qfiwater. islbei'ngQvvithdr-awn from. theboiler `5 in the .form of' steam ,.it i's obvious. that a.. variation inlevel of'water. in the b .oiler must. occur. Wherey there is a. constant'. differential maintained across thelva'lve 9T..

L The. Valve. d isla. differential. regulator valve.

Whichris. soJ designed as toimaintain: al definite Y but alterable.. diierence, in. pressure, across-the.

WaterJ level vcontrolled Q valve. 9;. The. manner-in Which. this is. accomplished., is'. as follows: rThe betweenpressurefrom the-d`own stream.. side off.

the valve Q and fa. second.Y pressure Whichf. can be altered .fas will'bepresently. described.j 'Ehe dew-nstream side of the vali/e Elfis connectedbyy means.

cfa-.conduit I5.to.a. chamber IIfw-hich is indi.- rect' communicationWithy one'. side of. the. diaphragm. Ill; Pressureisr supplied. to the other side of; the diaphragm. I4 through.- aA conduit I-l thatl leadsfr'om. the..up;stream.:-side. of thevalve-r 9, through a. .xed orifice. I 8! ito.. a bleed valve I 9;

A.. mercury column. consisting.V of thel mercury' connected inthe.. conduit I.`I.=between the orifice: I8` andlfthezbleed valve; I9 sor that@Y thee height.A`

ofthe mercury column is deducted from the pressure inthe conduit I'I below the aforesaid ori,

.position of'a valve head `I3in the Valve Sisconev l trolledA by a. diaphragm I4. vwhich .iszbalanced' flce, when this pressure is applied to the lower side of the diaphragm I4 through a conduit 23. With the bleed valve I9 closed, the pressure below the orice I8 becomes the upstream pressure of the valve 9 so that the height of the mercury column determines the differential pressure across the valve 9. Now, if the bleed valve I9 is opened so as to cause a drop in pressure across" the orice I8, this immediately causes a drop in the pressure on the lower side of the diaphragm I4 which causes the valve 8 to open thereby increasing the upstream pressure of the valve 9 until a balance is again restored. Thus, the position of the bleed valve I9 and its port area considered with respect to the port area of the orifice I8 governsv the differential maintained across the valve 9 and thus governs the water iiow through this valve for any open position thereof.

. The bleed valve I9 is actuated by a steam iiow indicator connected at 2'I to the steam line 6. A steam flow indicator 26 alsocontrols the air pressure from an air line to a control device 24. The control device 24 acts to open the bleed valve I9 as the steam flow increases in the steam line 6. The control device 24 includes a manua ally operable member 28 by which the degree of opening of the bleed valve I9 may be adjusted.

The degree of opening of the valve I9 is thus varied in response to steam flow in the outlet 6. The steam flow in the outlet 6 is a measure of the feed water demand. f

It is believed to be evident from the foregoing description that a proper design of the port areas of the orice I8 and the valve I9 can be made to give a differential across the valve 9 which will vary in proportion to the amount of feed water necessary to supplyv the steam being drawn through the outlet 6. Roughly, this means that the diiferential pressure across the Valve 9 should vary at a rate proportional to the square of the steam demand. With such a. proportional arrangement, the rate of feed water supplied to the boiler by means of the valve 9 is in direct proportion to the steam outlet provided the port' area of the valve 9 remains constant. Thus no change in level becomes necessary to alter the rate of feed water supply to accommodate for changes in steam demand. An extremely close range of water level can be maintained by this system over a wide range of steam demand. The water level regulator becomes less of a control valve Yand more of an auxiliary emergency protection which operates in the event of failure of the steam demand responsive device.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A boiler feed water control system comprising a feed water conduit, a valve therein, means responsive to thelevel of feed water in said.

boiler for controlling the position of said valve, andk means for varying the pressure differential across said valve automatically responsive to a desired governing factor in the operating process, said means comprising a diierential regulator in the feed water conduit including a valve in said feed water conduit and in series with the first named valve, a diaphragm controlling said last named valve, means for balancing said diaphragm between the pressures above and below said first named valve including conduits from said feed water conduitto the opposite sides of said diaphragm, a mercury column in one of said last named conduits arranged to compensate for a.

`"sponse to the desired governing factor.

2.` In asystem of the character described, a boiler, a liquid supply conduit therefor, and means responsive to liquid level in said boiler and rate of uid withdrawal from said boiler for controlling the flow of liquid in said supply conduit, said means including a valve in the liquid supply conduit, means to vary the port opening of said valve in response to liquid level variations in said boiler and a differential regulator comprising a valve in said liquid supply conduit in series with said first named valve,I a diaphragm controllingl` said last named valve, means for balancing said diaphragm between the pressures above'and below said first named valve, including conduits from said supply conduit to the opposite sides of said diaphragm, means in 'one of said last named conduits providing a fixed pressure differential between the diaphragm and said liquid supply conduit, and a bleed orifice in the conduit from the upstream side of said first named valve to the diaphragm, said bleedv orifice being adjustable in response to the rate of fluid withdrawal from the boiler. y

3. In a system `of the character described, a boiler, a liquid supply conduit therefor, and means responsive to liquid level in said boiler and rate of iiuid Withdrawal from said boiler for controlling the flow of liquid in said supply conduit, said means including a valve in the liquid supply conduit, means to vary the port opening of said valve in response to liquid level variations in said boiler and a differential regulator cornprising a valve in said liquid supply conduit in series with said first named valve, a diaphragm controlling said last named valve, means for balancing said diaphragm between the pressures above and below said rst named valve, including conduits from said supply conduit to the opposite sides of said diaphragm, and a bleed orifice in the conduit from one side of said first named valve to the diaphragm, said bleed orifice being adjustable in response to the rate of iiuid withdrawal from the boiler.

' 4. A boiler feed water control system comprising a feed water conduit, a valve therein, means responsive to the level of feed water in said boiler for controlling the position of said valve, and means for varying the lpressure differential across said valve automatically responsive to a desired governing factor in the operating process, said means comprising a differential regulator in the feed water conduit including a 'valve in said liquid supply conduit in series with the first named valve, a diaphragm controlling said last named valve, means for balancing said diaphragm between the pressures above and below said rst named valve including conduits from said liquid supplyconduit to `the opposite sides of said diaphragm, and a bleed orifice in the conduit fro-m the upstream side of said iirst named v alve to a point of lower pressure, said bleed orifice being adjustable in response to the desired governing factor.

' KENNETH BIHOWELL. 

